Posts Tagged ‘pressure vessel design’

Over the last few weeks we looked at the dangers associated with pressurized containers, also known as “pressure vessels.” We also looked at overpressure devices that can keep the pressure from building to the point where the vessel ruptures. But what about keeping pressure vessels from rupturing under normal operating pressure? You know, pressures well below the point where an overpressure device would kick in. This can happen if there is some sort of weakness in the pressure vessel caused by things like poor design, defective materials, or bad welds.

In the 19th Century the machines of the Industrial Revolution were driven by steam. Those magnificent machines advanced our civilization and standard of living. Sounds like a win-win situation, right? Wrong! The downside was that there were no standards for the design of pressure vessels like air storage tanks and boilers. Every engineer had their own ideas as to how they wanted to approach pressure vessel design. I use the word “engineer” loosely because most “engineers” of that time were not college graduates. Some approaches were good, some were bad, and some were in between. The end result was often not good. There were many pressure vessel leaks and explosions that damaged property, caused injury, and took lives.

By the turn of the 20th Century industrialization spread far and wide, intensifying safety concerns about pressure vessels. One deadly incident was the straw that broke the camel’s back. On March 10, 1905, the boiler failed in a shoe factory in Brockton, Massachusetts. 58 people were killed and another 117 were injured. The factory was completely destroyed. This tragedy prompted Massachusetts to form a Board of Boiler Rules to write boiler laws. Ohio followed with their own boiler laws. This was a step in the right direction, but each state law was different and a boiler that was legal in one state was illegal in another. There was no standardization between states.

In 1911 the American Society of Mechanical Engineers (ASME) formed its Boiler and Pressure Vessel Committee to address the lack of standardization. The committee’s work resulted in publication of the Boiler and Pressure Vessel Code (BPVC). In a nutshell, the BPVC establishes standardized rules governing the design, fabrication, testing, inspection, and repair of boilers and other pressurized vessels and containers. The BPVC set the standards that can be adopted by all states to minimize risk to the public.

The ASME is not a government agency, so it cannot enforce compliance with the BPVC. As a matter of fact, compliance with the BPVC by manufacturers has been completely voluntary. However, most state laws now require that pressure vessels must be certified by their manufacturers to be in compliance with the BPVC before they can be sold and put into operation. A certified pressure vessel must be permanently and conspicuously marked with the manufacturer’s name, the date built, serial number, and information about its construction and the type of use it’s designed for.

That wraps it up for our series about pressurized containers. Next time, we’ll shift gears and take a look at the project triangle and how it influences the outcome of engineering designs.